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Wed, 24 Jun 2026 14:21:11 +0000 (GMT) Received: from [9.43.75.139] (unknown [9.43.75.139]) by smtpav05.dal12v.mail.ibm.com (Postfix) with ESMTP; Wed, 24 Jun 2026 14:21:11 +0000 (GMT) Message-ID: Date: Wed, 24 Jun 2026 19:51:10 +0530 Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] null_blk: cancel bw_timer on add-device error unwind To: Cen Zhang , Jens Axboe , Keith Busch , Johannes Thumshirn , Chaitanya Kulkarni , Damien Le Moal , Genjian Zhang , Hans Holmberg , Kees Cook , Matthew Wilcox , Christophe JAILLET , Kyungchan Koh , Shaohua Li Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, baijiaju1990@gmail.com References: <20260624071825.357098-1-zzzccc427@gmail.com> Content-Language: en-US From: Nilay Shroff In-Reply-To: <20260624071825.357098-1-zzzccc427@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Authority-Analysis: v=2.4 cv=I4VVgtgg c=1 sm=1 tr=0 ts=6a3be7de cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=IkcTkHD0fZMA:10 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=VnNF1IyMAAAA:8 a=69x5WEd-yEzwNFSAJsQA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjI0MDExOSBTYWx0ZWRfXwOuQtr+0Xr7j qKvF8+CUgbZq+pnYa8YFAOp36JhrOpsScNlHOy4AdLnANrT+syb4yg+mV/ISTuO+yn+iHBMs0Gy iQvP+jUtE7itBEit7rLET7sHCt7MROr0nwhQ3tA50Hx36dsYVTjXbqhYH/Pse/6WwoviCHUTM4W QgOFz7d7C92TA77blHoFSgIygmsaFCc9V6AFki+zlJlMsQvh6cEe8nM07WIqcZDZNdxk6C3PpQ8 FDQqtEnxE+MFlT28p/iZMlDVXg0bcs5J+10u+d21lYuMQg3swF1Ck7OiIi/q0OvbkYyoA5MqWSO TcuL0U9tNdDP0WW+L4dfKvdDJGnhVlS80RnY1R791Z+ls8N/EenqJnomB6w9GfV/OP5saI3mz3n FO8FOI7ALLVSb2qg3g/E2urCr00AlQ== X-Proofpoint-GUID: 4aX1a0fftmsitd28-Wypkh-OrUBkLk66 X-Proofpoint-Spam-Info: AW1haW4tMjYwNjI0MDExOSBTYWx0ZWRfX9HOK/m60DZeS CgeE+Dp3r1tt4TJ9c5z002W82Iia4qtQJvuF88eVe80u/qegwiq3ZQ4E3NG+h+PbWm8uE+Xj9se s8VZ8I/BgFoCm9StRhy0QKl8syOOF5g= X-Proofpoint-ORIG-GUID: W2wlyhpBFGJ4AaP6mnBsaYqGcy5dQZbi X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-06-24_03,2026-06-23_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2606240119 On 6/24/26 12:48 PM, Cen Zhang wrote: > null_blk starts the bandwidth hrtimer before the later add_disk/device_add > failure points. If setup fails after the timer is queued, the shared error > unwind frees struct nullb without draining bw_timer, so the callback can > run on freed owner state. > > The buggy scenario involves two paths, with each column showing the order > within that path: > > null_add_dev() error unwind: nullb_bwtimer_fn() callback path: > 1. Start bw_timer for a throttled 1. The hrtimer expires after the free. > device. 2. nullb_bwtimer_fn() recovers the > 2. Hit a later add_disk/device_add embedded owner. > failure. 3. The callback reads nullb->dev and > 3. Free struct nullb. nullb->q. > 4. Release the remaining queue and 4. The stale owner storage is used > disk resources. after free. > > Cancel bw_timer in the shared error unwind before put_disk() and the > remaining frees. The normal delete path already uses the same > hrtimer_cancel() drain. Looks good to me. Reviewed-by: Nilay Shroff